The use of surgical staples to construct intestinal anastomosis is known. In an anastomotic stapling surgery, usually two pieces of tubular tissue are attached together by a ring of staples. Various anastomotic techniques are known including attaching the two pieces of tubular tissue end to end, end to side, and side to side. During construction of stapled end to end, or end to side anastomosis, a circular stapling device is often used. Circular stapling devices are most often used for colon and rectal surgery, whereby a diseased portion of the bowel is removed and the proximal and distal intestinal segments are joined together by means of a circular stapler to reestablish intestinal continuity. A circular stapling device may generally include a head assembly, a stapling assembly, a shaft assembly, a handle assembly, and a head base. In performing an anastomosis with such a stapling instrument, the two pieces of tubular tissue are clamped together between an anvil that has a circular array of staple-forming grooves and a staple holder that has a plurality of staple-receiving slots arranged in a circular array in which the staples are received. A staple pusher is advanced to drive the staples into the tissue and form the staples against the anvil. Present circular anastomosis stapling instruments include, for example, U.S. Pat. No. 5,205,459 to Brinkerhoff et. al. and U.S. Pat. Nos. 4,576,167 and 4,646,745 to Noiles, each of which is hereby incorporated herein by reference in its entirety.
Sometimes, a circular anastomosis stapling instrument may be provided with a flexible shaft that allows the head assembly to assume various positions relative to the actuator assembly. For example U.S. Pat. No. 4,473,077 to Noiles et. al., U.S. Pat. No. 4,754,909 to Barker et. al., and U.S. Pat. No. 4,488,523 to Shichman, each of which is hereby incorporated by reference herein in its entirety, disclose circular stapling instruments with flexible shafts.
One method of constructing an anastomosis includes a double purse string suture technique. In preparation for the anastomosis, purse string sutures are placed in both the proximal and distal ends of the lumen to be connected. Typically, the anvil is secured in the proximal bowel, and the circular stapler with the anvil detached is inserted into the anal opening of the patient and up through the appropriate length of rectum. During passage of a circular stapler without the anvil portion attached, the attendant bowel may be traumatized and or irritated by blunt, sharp, cornered, etc. surfaces of the stapling assembly. At other times, the circular stapler with the anvil detached may not be able to negotiate the bowel with relative ease because of strictures in the walls of the bowel and naturally occurring intestinal valves and curves.
In another version of the double purse string suture technique, a circular stapler, with the anvil attached, is passed through the anus to the distal end of the lumen, which has been secured by a purse string suture. The purse string suture must then be opened wide enough to allow the entire anvil to be extended through the distal end of the lumen and into the proximal end of the lumen. The distal purse string suture is then pulled tight, gathering the tissue about the extended trocar, and the proximal purse string suture is pulled tight, gathering the tissue about the anvil shaft. The actuator is then engaged, which brings the anvil and the stapling assembly together, resulting in a ring of staples about the perimeter of the now connected lumen. When the circular stapler is passed through the intestinal tract as one unit, as in this technique, the need to open the distal purse string suture wide enough to allow the anvil to pass through the end of the distal lumen may result in intestinal content spillage, which may lead to increased rates of postoperative infection. Even with the anvil attached to the stapler, the shape of the anvil may not be streamlined, and trauma to the intestine may occur when the stapler is passed through the intestinal tract.
Another technique of constructing an anastomosis includes using a purse string suture at the proximal end of the lumen and staples at the distal end of the lumen. This type of anastomosis is often referred to as a double staple technique. This method can be advantageous because it does not require the placement of a purse string suture about the end of the distal lumen, which can be difficult to apply and, as stated above, may result in intestinal content spillage. Otherwise, this technique is performed in generally the same manner as the first method described above for the double purse string technique, whereby the stapler with the anvil detached is inserted through the anus to the distal end of the lumen, and the anvil is inserted in the proximal end of the lumen. The same limitations as the earlier described technique are attendant in this technique, namely that the passage of the circular stapler without the anvil, may cause bowel irritation and or trauma. Further, the stapler, without the anvil may be difficult to negotiate through the intestinal tract due to strictures, and or naturally occurring curves, twists, and valves.
As more colon and rectal procedures are performed laparoscopically, a need in the art exists for a circular stapler that can be more easily passed through the bowel when the anvil is not attached. There exists a need in the art for a retractable cover or shield to facilitate passage of a surgical stapler through the intestinal tract, allowing the surgeon to minimize or avoid trauma to the intestinal tract during insertion of the stapler, and to negotiate and dilate intestinal strictures. There also exists a need in the art for a surgical stapler including an air or gas pump assembly that can be used to insufflate the rectum and intestinal tract during insertion and advancement of the stapler.